The ectotympanic, or tympanicum, is a bony structure found in all mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In catarrhine primates (including humans), it takes a tube-shape.^[1][2] Its position and attachment to the skull vary between primates, and can be either inside or outside the auditory bulla.^[3][4]

It is homologous with the angular bone of non-mammalian tetrapods. When the latter is present, it contacts the entotympanic.^[5]

• webref: Anthropology Archived 2012-02-12 at the Wayback Machine
• Hershkovitz P (1974). "The Ectotympanic Bone and Origin of Higher Primates" (PDF). Folia Primatologica. 22 (4): 237–42. doi:10.1159/000155628. PMID 4218574.
• Jones FW, Lambert VF (October 1939). "The occurrence of the lemurine form of the ectotympanic in a primitive marsupial". J. Anat. 74 (Pt 1): 72–5. PMC 1252559. PMID 17104802.

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